Guns, Ammo, Bomb Instructions : Should There Be A Limit To What’s Available On The Internet?

A person can buy literally anything off the internet these days.  From detailed instructions on how to build a a bomb to thousands of rounds of ammo or hand guns to anthrax and nerve gas.  Question, why would the average person need to know how to build a bomb?   Would the shooting at the Colorado movie theater have turned out different had the shooter not been able to buy the ammo online?  Or was this just an isolated incident?  Should access to certain things be bane from the internet?